478 KECOKD OF SCIENCE FOR 1887 AND 1888. 



not a necessary coustituent. He gives C28H47N3O6 as the formula for 

 pbyllocyanic acid. Schunck has also studied the chemistry of cliloro- 

 pbyle (Proc. Roy. Soc. Lond., XLii). Hausen states (Arbeit. lust., 

 Wiirzburg, ill) that the oraugered i)igmeut reported to have been 

 observed in leaves is only an aggregation of the yellow chloroi)hyll 

 pigmeut, which has an oraugetint wheu present iu deuse masses. Epi- 

 dermal chlorophyll has beeu further studied by Moore (Journ. Bot., 

 XXV) and the preparation of pure chlorophyll described by Macchiati 

 (Malpighin, i), Peyfon (Compt. Rend., cv), has devised an iustrumenf; 

 with which he has iuvestigated the hourly variatiou iu the action of 

 chlorophyll, findiug that the fuuction at different hours in the day is 

 proportional to the intensity of light. 



Nuuierous other cell-conteuts have beeu studied. Hillhouse (Midi. 

 Nat., X and xi) has investigated the fuuction of tauuiu, aud finds that 

 it is not used in the process of growth after its production, and it can 

 not therefore be regarded as a food material. Fribosin is described by 

 Zopf (Ber. deutsch. Bot. Gesell., v) as a new cell-content, found in the 

 conidia of Podosphcera, Sphccrotheca aud Erysiplie. The formation of 

 oxalate of lime in leaves has been investigated by Schimper (Bot. Zeit,, 

 XLVi), aud the formation of calcium oxalate by Wakker (see Bot. Cen- 

 tral bl., xxxiv). In regard to the acid secretion from the roots of plants 

 Molisch states (Sitzb. K. K. Zool. Bot. Gesell., Wien, xxxvii), that it 

 attacks organic substances even more powerfully than inorganic, aud 

 not only dissolves them but induces other important chemical changes. 



The use of histological elements as a means of classification has been 

 further iuvestigated during the year, and while no comprehensive dic- 

 tum can yet be laid down, substantial progress has beeu made, ai.d the 

 prospect is that when all plants have been thoroughly iuvestigated 

 distinctive characters will be detected. Hildebrandi, for example, has 

 examined a large number of species of Ambrosiew and Senecionidecs 

 (Beitr. Z. vergleich. Anat. der Arabros. u. Senec. Inaug. Diss.) and con- 

 cludes that they may be very clearly distinguished by the histological 

 elements. Jiiunicke (Bot. Centralbl.,xxxi) also concludes that the three 

 genera of the Geraniacece examined by him can be distinguished from one 

 another by characters derived from the structure aud distribution of the 

 vascular bundles iu the leaf and flower-stalks. Juel (Bot. Centralbl., 

 xxxiii) has studied the anatomical structure of the Marcgraviacem, and 

 Solereder (see Bot. Centralbl., xxxiii) has discussed "The systematic 

 value of the perforation in the walls of vessels," and Wible has a paper 

 " Zur Diagnostic des coniferen Holzer." On the other hand, Plitt (Beitr. 

 z. vergleich. Anat. d. Blattstieles d. Dikotyledoneu) has examined the 

 petiole or leaf-stalk of two hundred and eighty-three plants in thirty 

 natural orders for characters of systematic value and the results were 

 mainly negative, and Saupe (Flora, lxx) has investigated the wood of 

 Lefinminosea; and finds that the division into the sub-orders Papilion- 

 aciv Cesidpimeff and Mmoseie does not correspond to structural differ- 



